Inhalation therapy device

ABSTRACT

The invention relates to an inhalation therapy device including a membrane aerosol generator. A detection device is provided for determining whether a liquid to be atomized is available. In the absence of liquid, the activation of the membrane aerosol generator is interrupted and/or a signal is output.

The invention relates to inhalation therapy devices having anoscillatable membrane for nebulising a liquid.

Known from the patent specification DE 199 53 317 C1 is an inhalationnebuliser of the type described above. The aerosol membrane generatordescribed therein comprises a cylindrical liquid storage container whichis delimited at one end face by a membrane having the shape of acircular disc.

A liquid disposed in the liquid container touches the side of themembrane facing the liquid storage container. DE 199 53 317 C1furthermore describes an oscillation generator, for example a piezocrystal, which surrounds the membrane in a circular manner and isconnected thereto such that the membrane can be caused to oscillate bymeans of the oscillation generator and an electric drive circuit.

The liquid abutting the membrane on the one side is conveyed throughholes in the oscillating membrane to the other side of said membrane andis emitted on this side into the mixing chamber as an aerosol.

Known from the utility model DE 295 01 569 is an ultrasonic liquidnebuliser having a piezo crystal which is caused to oscillateelectrically by an oscillator circuit, said oscillator circuit beingsupplied by a power supply device.

DE 295 01 569 describes an oscillator circuit which comprises a currentlimiting circuit and which is connected with an electronic temperaturelimiting circuit that compares a temperature-dependant electric signaloccurring at the piezo crystal in a threshold circuit, the comparisonsignal of which activates a bistable circuit which blocks the oscillatorwhen a limiting temperature in the piezo crystal is reached.

The disclosure of DE 295 01 569 is thereby directed at a protectivemechanism for an ultrasonic liquid nebuliser in which the piezo crystalitself causes the liquid to oscillate and is in contact with acomparatively large amount of liquid. The liquid nebuliser described inDE 295 01 569 must furthermore accordingly use large currents in orderto cause the large amount of liquid to oscillate.

Constant contact between the piezo crystal and the liquid is necessaryowing to these large currents and the resulting large temperaturedifferences in order to prevent destruction of the piezo crystal. Ifthere is no longer any liquid present, the piezo crystal heats up veryquickly and is destroyed if the oscillating circuit driving thenebuliser is not switched off immediately.

Only much smaller currents flow in inhalation nebulisers of the typedescribed at the beginning of this document, i.e. in inhalationnebulisers having membrane aerosol generators, and therefore onlycomparatively small temperature differences occur. In such inhalationnebulisers, the lack of liquid does not directly lead to heat-relateddamage to the piezo-electric elements. However, if a membrane inhalationnebuliser runs without a load, this can, on rare occasions, cause themembrane to break.

However, it is also necessary in inhalation nebulisers having a membranegenerator to reliably detect the presence of a liquid to be nebulised.This is because, on the one hand, the basis for a very high dosageaccuracy is thereby created and, on the other hand, it is possible toreliably indicate the end of a therapy session to the patient.Furthermore, by immediately disconnecting the inhalation therapy device,it is possible, for example, to save a battery.

Therefore, the use of a protective mechanism such as described in DE 29501 569 is not necessary in inhalation nebulisers of the type in questionhere and is not possible either owing to the much smaller currents andtemperature alterations.

The object of the present invention is therefore to configure aninhalation therapy device having a membrane aerosol generator and acorresponding method such that it is possible to reliably detect whetheror not a liquid is present in the liquid reservoir of the inhalationtherapy device.

This object is solved by an inhalation therapy device according to claim1.

Such an inhalation therapy device comprises an oscillatable membrane fornebulising a liquid, an oscillation generating device which has at leastone connecting means for supplying an activation signal and by means ofwhich the membrane is caused to oscillate when the activation signal issupplied such that a liquid disposed on one side of the membrane isnebulised through said membrane and is present on the other side of themembrane as an aerosol, and a control means from which an activationsignal can be supplied to the at least one connecting means of theoscillation generating device such that the oscillation generatingdevice causes the membrane to oscillate, characterised in that adetection device is provided which detects at least one electricparameter of the oscillatable structure comprising the membrane and theoscillation generating device and which determines the presence of aliquid to be nebulised based on the at least one parameter.

The object is furthermore solved by an inhalation therapy methodaccording to claim 9.

Such an inhalation therapy method for an inhalation therapy devicecomprises the following steps:

switching on the inhalation therapy device;

supplying activation signals from the control means to the oscillationgenerating device in order to nebulise the liquid;

detecting at least one electric parameter of the oscillatable structurecomprising the membrane and the oscillation generating device; and

determining whether or not liquid is still present based on the detectedparameter of the oscillatable structure.

The invention enables a greater dosage accuracy of the medicament forthe patient, allows the patient to concentrate better on the therapy andincreases the user-friendliness of the inhalation therapy device, notleast owing to a longer running time during battery operation.

Due to the possibility of determining whether or not liquid is stillpresent, it is possible to automatically switch off the inhalationtherapy device and/or to indicate to the patient that there is nomedication left in the inhalation therapy device. This can also occurright at the start of a therapy session. However, in particular, thepatient does not have to constantly check during the therapy sessionwhether there is any medication left. The user-friendliness of theinhalation therapy device is thereby increased and the therapy is lessbothersome for the patient.

Furthermore, detection of the at least one electric parameter means thatthe battery capacity can be saved and that it can be determined whetherthere is a bad contact in the inhalation therapy device or whetherdroplets have formed on the membrane, which affects the nebulisingproperties of the device. A worse TOR (Total Output Rate) is furthermorealso recognised.

However, above all, the accuracy of the dose of the inhalation substancecan be improved by the invention and the patient can concentrate betteron the therapy, which leads to improved treatment success.

The formation of droplets on the membrane can occur during operation ofthe inhalation therapy device or the membrane can become clogged. Theoccurrence of these two phenomena leads to a deterioration of thenebulising properties of the device.

It is, however, possible for the inhalation therapy device to recogniseboth phenomena since both droplet formation and clogging of the membranechange the at least one detected electric parameter of the oscillatablestructure in a characteristic manner. Countermeasures (e.g. switchingoff the device) can thereby be taken in good time.

Further advantageous embodiments of the invention can be seen in thesub-claims.

The invention will be described in more detail below by means ofembodiments examples as shown in the figures, from which furtheradvantages and features of the invention arise.

FIG. 1 shows a schematic representation of an inhalation deviceaccording to a first embodiment example,

FIG. 2 shows a flow diagram which graphically represents a method fordetermining the presence of liquid in the inhalation device according toa first embodiment example,

FIG. 3 shows a schematic representation of an inhalation therapy deviceaccording to a second embodiment example,

FIG. 4 shows a flow diagram which graphically represents a method fordetermining the presence of liquid in the inhalation device according toa second embodiment example, and

FIG. 5 shows an example of the progression over time of a measuringcurve of a detected electric parameter when using two differentoscillation frequencies for the membrane according to a secondembodiment example.

Referring to FIGS. 1 and 2, the invention will now be explained in moredetail below by means of a first embodiment.

FIG. 1 shows an inhalation therapy device according to the invention, inwhich in a nebuliser unit A, a liquid (3) stored in a liquid reservoir(2) is nebulised by means of a membrane (1) into a nebulisation cavity(4).

Nebulisation then occurs when the membrane (1) is caused to oscillate.For this purpose, the membrane (1) is attached to a support unit (6)which supports the membrane (1) and to which an electromechanicaltransducer unit (7), for example a piezo element, is also attached.

The membrane (1), the support unit (6) and the electromechanicaltransducer unit (7) are configured in a rotationally symmetrical mannerin the embodiment described here and together form an oscillatablestructure.

An activation signal of a control means (10) can be supplied to theelectromechanical transducer unit (7) via connecting lines (8, 9), saidcontrol means being accommodated in a separate control unit B in theembodiment described here. When the activation signal is supplied, theoscillatable structure (1, 6, 7) is caused to oscillate and the liquid(3) is nebulised through the membrane (1).

A patient can inhale the aerosol provided in the nebulisation cavity (4)at the mouthpiece (11) of the nebuliser. So that a sufficient amount ofair is supplied, one or more air holes (12) are provided in the housingof the nebuliser, through which ambient air can enter into the cavity(4) during inhalation and out of which the air inhaled by the patientcan exit from the cavity (4) during exhalation.

Different electrical properties of the oscillatable structure (1, 6, 7)(e.g. current, voltage, phase shift) are dependant in particular on thecapacity of the electromechanical transducer unit (7). The oscillatablestructure (1, 6, 7) displays very specific characteristics duringnebulisation and during operation without liquid, which are reflected inthe electric parameters of the oscillatable structure. The operatingstates with and without liquid on the membrane can be reliablydetermined by means of these electric parameters. Current consumption(current), power consumption (power) and the current/voltage phase shift(phase position) are particularly suitable as electric parameters.

In order to detect at least one of the electric parameters, a detectiondevice (13) is provided according to the invention, which is configuredand is connected with the oscillatable structure (1, 6, 7) and/or thecontrol means (10) such that the at least one electric parameter issupplied to the detection device (13). For this purpose, the connectinglines (8, 9), for example, are configured such that during operation ofthe control unit (10), at least one electric parameter of theoscillatable structure (1, 6, 7) is transmitted to the detection device(13) via the connecting lines (8, 9) and can be detected thereby.

The invention is based on the surprising possibility of being able todraw conclusions with regard to the operating state as a result of thedetection of at least one electric parameter of the oscillatablestructure (1, 6, 7) (e.g. voltage tap, current consumption or thecurrent/voltage phase position at the piezo crystal of the membrane)owing to the characteristics of the oscillatable structure (1, 6, 7) andit can thereby be determined whether or not liquid (3) is still presentin the liquid reservoir (2).

Detection of the at least one electric parameter of the oscillatablestructure (1, 6, 7) by the detection device (13) can occur continuouslyor at discrete time intervals.

Determination of the operating state, i.e. determination of whetherliquid is present or not, preferably occurs in the detection device (13)by comparing the detected value of the at least one parameter with avalue for this parameter stored in said detection device. The detectiondevice (13) comprises, for example, a memory (13 a) for this purpose.

If, by comparing a detected value with a stored value, the detectiondevice (13) determines that there is no more liquid (3) stored in theliquid reservoir (2), the detection device (13) then emits, in apreferred embodiment, a signal to the control means (10), which in turnautomatically stops the supply of activation signals to the oscillatablestructure (1, 6, 7), i.e. automatically switches off the inhalationtherapy device.

In an alternative embodiment, the detection device (additionally) emitsan optical or audio signal to indicate to the patient that theinhalation therapy device has consumed the stored liquid (3) in theliquid reservoir (2), which signals the end of the therapy session tothe patient. For his part, the patient can then switch off theinhalation therapy device if automatic switching off is not provided inaddition to the optical/audio signal.

The inhalation therapy device comprises a signal emitting means (14) foremitting the audio/optical signal, which is connected with the detectiondevice (13) (or alternatively the control means).

The audio signal emitted for this purpose can be a short sound signal of0.5 to 2 seconds in length. These audio signals are, however, not justrestricted to notes, rather sound sequences or recorded or synthesisedvoice signals can also be used.

FIG. 2 shows a flow diagram, by means of which a possible course of atherapy session will now be described.

By switching on the inhalation therapy device (step S1), activationsignals are supplied to the oscillatable structure (step S2).Immediately afterwards, the detection device (13) verifies whether theinitial conditions for a therapy session exist, i.e. it determineswhether liquid (3) is present in the liquid reservoir (2).

More precisely, the detection device (13) detects at least one electricparameter of the oscillatable structure (1, 6, 7) (step S3) anddetermines, based on the detected value of the at least one electricparameter, whether liquid is present or not (step S4).

For this purpose, the detection device (13) reverts, for example, toempirically determined values for the detected electric parameter, whichare stored in a suitable manner in the detection device, for example inthe semiconductor memory (13 a) shown in FIG. 1, or uses a value of theat least one parameter which was detected in a previous cycle of theloop (see below). This value is stored in a suitable form by thedetection deivce (13) for this purpose, for example in the semiconductormemory (13 a).

If the presence of liquid is determined by a comparison of the values(step S5), the activation signal continues to be supplied to theoscillatable structure (1, 6, 7); the control sequence then returns tostep S2.

If, on the other hand, it is determined in step S5 that no liquid ispresent, supply of the activation signal to the oscillatable structure(1, 6, 7) is immediately stopped again (step S6). An optical/audiosignal can be additionally or alternatively emitted (step S6).

The loop of steps S2 to S5 is performed continuously or at regularintervals (discrete time steps) in order to verify the presence ofliquid during the therapy session and, if necessary to stop the supplyof the activation signal to the oscillatable structure, and thus to stopnebulisation.

A second embodiment example of the invention will now be explained bymeans of FIGS. 3 to 5.

FIG. 3 shows a second embodiment example of an inhalation therapydevice, in which at least two different oscillation frequencies for themembrane are generated and are alternatingly supplied to the membrane.The first frequency f₁ is the activation frequency which is supplied tothe oscillatable structure (1, 6, 7) in order to cause the membrane tooscillate and to nebulise the liquid. The second frequency f₂ on theother hand is a frequency used for determining the operating state ofthe oscillatable structure (1, 6, 7). The time periods in which thesecond frequency f₂ is supplied to the oscillatable structure (1, 6, 7)are typically much shorter than the time periods in which the firstfrequency f₁ is supplied. This is because the second frequency f₂ issupplied for measuring purposes and may only disturb the generation ofthe aerosol to the smallest extent possible.

As shown in FIG. 3, the control unit (10) comprises, for example, anoscillator (20) for this purpose in this second embodiment, which cangenerate at least two different oscillation frequencies (f₁, f₂) for themembrane (1).

A switching means (21) switches the oscillator (20) of the control unit(10) between the normal operating frequency f₁ and the measuringfrequency f₂ at predetermined times, the inhalation therapy devicenebulising the available liquid during the intervals in which the normaloperating frequency f₂ is used.

The detection unit (13) stores the detected values of the at least oneelectric parameter which were detected when using the measuringfrequency f₂ in order to be able to analyse these measured values alsoover a longer period of time.

Determination of the operating state, i.e. determination of whetherliquid is present or not, then occurs in the detection device (13)either by comparing a value of the at least one parameter that wasdetected during the normal operating frequency f₁ with a value for thisparameter that is stored in the detection device (the detection device(13) comprises, for example, a memory (13 a) for this purpose), or byevaluating values of an electric parameter that were recorded when usingthe measuring frequency f₂. The operating state can, of course, also bedetermined by using values of both sets of detected parameters.

It is furthermore also possible to record the values of the electricparameter detected during the normal operating frequency f₁ in thedetection device (13) (for example in a memory (13 b)) in order to alsobe able to analyse these over a longer period of time.

If the detection device (13) determines that no more liquid (3) isstored in the liquid reservoir (2), the detection device (13) then, in apreferred embodiment, emits a signal to the control means (10), which inturn automatically stops the supply of activation signals to theoscillatable structure (1, 6, 7), i.e. automatically switches off theinhalation therapy device.

Reference is furthermore made to that stated above with regard to thefirst embodiment example.

FIG. 4 shows a flow diagram, by means of which a possible course of atherapy session according to the second embodiment will now bedescribed.

By switching on the inhalation therapy device (step S1), activationsignals having a normal operating frequency f₁ are supplied to theoscillatable structure (step S2).

Immediately afterwards, the detection device (13) verifies whether theinitial conditions for a therapy session exist, i.e. it determineswhether liquid (3) is present in the liquid reservoir (2).

More precisely, the detection device (13) detects at least one electricparameter of the oscillatable structure (1, 6, 7) when using the normaloperating frequency f₁ (step S3) and determines, based on the detectedvalue of the at least one electric parameter, whether liquid is presentor not (step S4).

For this purpose, the detection device (13) reverts, for example, toempirically determined values for the detected electric parameter, whichare stored in a suitable manner in the detection device, for example inthe semiconductor memory (13 a) as shown in FIG. 3.

If the presence of liquid is determined (step S5), the activation signalcontinues to be supplied to the oscillatable structure (1, 6, 7); thecontrol sequence then returns to step S2.

If, on the other hand, it is determined in step S5 that no liquid ispresent, supply of the activation signal to the oscillatable structure(1, 6, 7) is immediately stopped again (step S6). An optical/audiosignal can be additionally or alternatively emitted (step S6).

Following the initialisation step, the loop of steps S2 to S5 isperformed continuously or at regular intervals (discrete time steps) inorder to verify the presence of liquid during the therapy session and,if necessary to stop the supply of the activation signal to theoscillatable structure and thus nebulisation. Switching between thenormal operating frequency f₁ and the measuring frequency f₂ is therebycarried out at predetermined intervals. The length of the time intervalsduring which the measuring frequency f₂ is used are selected such thatthe nebulising operation is not disturbed. The time intervals of themeasuring frequency are typically smaller by at least a factor of 10.

More precisely, the detection device (13) detects at least one electricparameter of the oscillatable structure (1, 6, 7) during use of thenormal operating frequency f₁ (step S3) or the measuring frequency f₂(step 3′) and determines, based on the detected values of the at leastone electric parameter, whether liquid is present or not (step S4).

For this purpose, the detection device (13) reverts, as regards thevalues detected using the normal operating frequency f₁ (step 3), eitherto empirically determined values for the detected electric parameter,which are stored in a suitable manner in the detection device, forexample in the semiconductor memory (13 a) as shown in FIG. 3, or uses avalue of the at least one parameter which was detected in a previouscycle of the loop. This value was stored for this purpose in a suitableform by the detection device (13), for example in the semiconductormemory (13 a).

The detection device (13) evaluates the detected values of the at leastone electric parameter of the oscillatable structure (1, 6, 7) that weredetermined during use of the measuring frequency f₂ and were stored inthe memory (13 b) (step 3′) either just like the other measured valuesor, preferably, over a longer period of time (step 4).

The decision as to whether or not liquid is present can be based in thisembodiment example on both types of detected values of the electricparameters. This increases the certitude of the accuracy of thedetermination of whether or not liquid is present. Furthermore, byobserving the course of the measuring curve over a longer period oftime, the reliability of the determination of whether or not liquid ispresent can be further increased.

The invention is, however, not restricted to the use of two frequencies.Several frequencies can be used for the described device.

FIG. 5 shows an example of the progression over time of one of thedetected electric parameters when two different frequencies are used forthe membrane oscillations.

An example measuring curve can be seen in FIG. 5, which shows theprogression of the detected values of the at least one electricparameter of the oscillatable structure (1, 6, 7) according to thesecond embodiment example. The measured value in the example measuringcurve is the current consumption of the oscillatable structure (1, 6, 7)in mA.

The progression over the time period of 0 to approximately 17 secondscan be attributed to the switching-on process and can be disregarded.

It can be seen over the entire range of the measuring curve that in thetime intervals in which an activation signal having the operatingfrequency f₁ is applied to the oscillatable structure, a value ofapproximately 1.6 mA initially occurs, which declines to a value of 0.9mA between the 80^(th) and 97^(th) second. This progression of themeasuring curve also corresponds to the basic progression of thedetected values in an embodiment of the invention in which only theoperating frequency f₁ is used.

The short time intervals in which an activation signal having themeasuring frequency f₂ is applied to the oscillatable structure (1, 6,7) can also be recognised in FIG. 5. These time intervals correspond tothe peaks recognisable in FIG. 5, and it is also clear that these timeintervals are shorter than the time intervals between the peaks in whichthe operating frequency f₁ is used.

In the time interval between the 15^(th) and the 85^(th) second, themeasured values detected for the operating frequency f₁ are in a verynarrow range of approximately 1.6 mA. After the 85^(th) second, themeasuring curve of the values decreases to approximately 0.9 mA for theoperating frequency f₁. After approximately the 97^(th) second, themeasured values are again essentially constant.

In the very brief time intervals in which the measuring frequency f₂ isused, the peak values are interesting, which increase over the entireprogression of the curve. In the time interval between the 15^(th) andthe 95^(th) second, the peak values proceed along a straight line with afirst gradient; in the period after the 95^(th) second, the peak valuesof the measured values for the measuring frequency f₂ proceed along astraight line with a second gradient which is greater than the firstgradient. This change in gradient is a clearly recognisable sign thatliquid is lacking on the membrane or on the oscillatable structure (1,6, 7) of the inhalation therapy device.

Thus, the second embodiment example of the inhalation therapy deviceaccording to the invention has two measuring curve progressions, usingwhich the lack of liquid can be determined. This is because, on the onehand, the measuring curve of the values for the operating frequency f₁declines when the liquid has been consumed and, on the other hand, therate of increase of the peak values of the values determined formeasuring frequency f₂ changes.

The measuring curve shown in FIG. 5 is just an example and can changefor different designs of the inhalation therapy device. In particular,the values and time periods specified can differ depending on thespecific configuration of the device.

1. An inhalation therapy device comprising an oscillatable membrane fornebulising a liquid, comprising an oscillation generating device havingat least one connecting means for supplying an activation signal and bymeans of which said membrane is caused to oscillate when the activationsignal is supplied such that a liquid disposed on one side of themembrane is nebulised through said membrane and is present on the otherside of the membrane as an aerosol, and comprising a control means fromwhich an activation signal can be supplied to the at least oneconnecting means of the oscillation generating device such that saidoscillation generating device causes the membrane to oscillate, whereina detection device is provided which detects at least one electricparameter of the oscillatable structure comprising the membrane and theoscillation generating device and which determines the presence of aliquid to be nebulised based on the at least one parameter, the at leastone electric parameter being the current consumption, the powerconsumption or the current/voltage phase shift.
 2. An inhalation therapydevice according to claim 1, Wherein the control means alternatinglygenerates activation signals with at least two different frequencies andthe detection device determines the presence of a liquid to be nebulisedbased on the detected values of the at least one parameter at the atleast two different frequencies.
 3. An inhalation therapy deviceaccording to claim 2, wherein at least one first activation signalhaving a first frequency causes nebulisation of the liquid.
 4. Aninhalation therapy device according to claim 2, wherein the timeintervals in which a first activation signal having a first frequency isgenerated are longer than the time intervals in which an activationsignal having a second frequency generated.
 5. An inhalation therapydevice according to claim 1, wherein the detected values are stored foran evaluation over a longer period of time.
 6. An inhalation therapydevice according to claim 1, wherein if the detection device determinesthat no liquid is present, said detection device prevents the supply ofactivation signals by the control means to the oscillation generatingdevice, and/or triggers the generation of an optical and/or audio signalby a signal emitting means in order to indicate that no liquid ispresent.
 7. An inhalation therapy device according to claim 6, whereinthe emitted audio signal is a short sound signal and/or a sound sequenceand/or recorded or synthesised voice signals.
 8. An inhalation therapydevice according to claim 1, wherein the oscillation generating devicecomprises an electromechanical transducer unit.
 9. An inhalation therapydevice according to claim 8, wherein the oscillation generating devicecomprises a support unit to which the electromechanical transducer unitand the membrane are attached.
 10. An inhalation therapy deviceaccording to claim 1, wherein an energy supply unit for the inhalationdevice is integrated in the control means.
 11. (canceled)
 12. Aninhalation therapy method for an inhalation therapy device according toclaim 1, comprising the following steps: switching on the inhalationtherapy device; supplying activation signals from the control means tothe oscillation generating device in order to nebulise the liquid;detecting at least one electric parameter of the oscillatable structurecomprising the membrane and the oscillation generating device; anddetermining whether or not liquid is still present based on the detectedparameter of the oscillatable structure, the at least one electricparameter being the current consumption, the power consumption or thecurrent/voltage phase shift.
 13. An inhalation therapy method for aninhalation therapy device according to claim 2, comprising the followingsteps: switching on the inhalation therapy device; supplying activationsignals having at least two different frequencies from the control meansto the oscillation generating device, the liquid being nebulised at atleast one frequency; detecting values of at least one electric parameterof the oscillatable structure comprising the membrane and theoscillation generating device at the at least two different frequencies;and determining whether or not liquid is present based on the values ofthe detected parameter of the oscillatable structure at at least one ofthe at least two different frequencies.
 14. An inhalation therapy methodfor an inhalation therapy device according to claim 12, wherein saidmethod further comprises the following steps: continuing to supply theactivation signals from the control means to the oscillation generatingdevice in order to continue nebulisation of the liquid if it isdetermined that liquid is present; and stopping the supply of activationsignals from the control means to the oscillation generating deviceand/or emission of an optical and/or audio signal if it is determinedthat no liquid is present.
 15. (canceled)
 16. An inhalation therapydevice according to claim 2, wherein the time intervals in which a firstactivation signal having a first frequency is generated are longer, byat least a factor of 10, than the time intervals in which an activationsignal having a second frequency is generated.
 17. An inhalation therapydevice according to claim 1, wherein the oscillation generating devicecomprises a piezoelectric element.